The onset of superconductivity in homogeneous ultrathin films is found to occur when their normal-state sheet resistance falls below a value close to h/4${e}^{2}$, the quantum resistance for pairs. The data further suggest that in the T\ensuremath{\rightarrow}0 limit such films are either superconducting or insulating. The existence of a threshold in systems which are not granular implies that its explanation involves more general arguments than those which follow from the modeling of films by Josephson-coupled arrays.
We study Cooper-pair tunneling in a voltage-biased superconducting single-electron transistor under microwave irradiation. By tracing the peak positions of a photon-assisted Jos...
Superconductivity can occur under conditions approaching broken-symmetry parent states1. In bilayer graphene, the twisting of one layer with respect to the other at ‘magic’ twis...
The guiding conception of vortex-condensation-driven Mott insulating behavior is central to the theory of the nodal liquid. We amplify our earlier description of this idea and s...
We have studied the effects of an exchange-enhanced substitutional impurity on a host metal by double-time Green's functions. We have used a simplification of the Wolff model to...
We have studied the quantized Hall effect of the two-dimensional electron gas in GaAs- ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterojunctions at low temp...
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